Galaxy was one of the first pulps to explicitly bill itself as a magazine for "adults," in 1950 under founding editor HL Gold.
I grew up on Galaxy, buying old issues for a quarter from the sale rack outside of Bakka, Toronto's stalwart sf bookstore. Later, I studied under Kate Wilhelm, who told uproarious stories about editing the magazine under Fred Pohl — I also spent a couple entertaining evenings getting Pohl's version of these stories.
The Internet Archive has nearly the entire run of Galaxy for your perusal, with classic stories by Le Guin, Cherryh, Heinlein, Bradbury, Asimov, Bester, and other pioneers. Also available is most of IF, Galaxy's sister magazine.
When Galaxy appeared in October 1950, it promised a kind of science-fiction different from the space operas of previous decades. As an "annual report" written by publisher H.L. Gold proclaimed,
…other publishers thought the idea of offering mature science fiction in an attractive, adult format was downright funny. They knew what sold–shapely female endomorphs with bronze bras, embattled male mesomorphs clad in muscle, and frightful alien monsters in search of a human soul.
And while Astounding Science Fiction was focused on technology–suited for an America that had fundamentally changed since WWII–H.L. Gold's Galaxy focused on ideas, humor, satire, psychology and sociology. It also had one of the best pay rates in the industry, and offered some of its writers exclusive contracts. And the writers responded in kind and followed their own obsessions–although Gold often pitched ideas.
[Ted Mills/Open Culture]